def add_two_numbers(a, b):
    return a + b
def subtract_two_numbers(a, b):
    return a - b

def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, n):
        if n % i == 0:
            return False
    return True

def is_prime1(n):
    if n <= 1:
        return False
    for i in range(2, int(n**0.5)+1):
        if n % i == 0:
            return False
    return True

#递归实现阶乘
def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)
    return factorial(n)
print(factorial(5))
print(is_prime(7))
print(is_prime1(7))